The rusted, iron-wrought gate clangs shut behind you. Heaving a sigh of relief, you eagerly anticipate the after-action report charting your achievements of another aced Dishonored mission. Alerts: none. Detections: zip. Enemies killed: one. Bodies fou—wait, one ?! You didn't lift your blade at all against the City Watch during that run, and you even ensured a shadowy dumping corner in the sewers for the unconscious. "The sewers," you quickly realize, an teeming with swarms of infested rats hungering for a fleshy meal. Whoops.

Dancing the detection disco in Dishonored often hinges success or failure upon a single decision or mistake rippling with a cascading effect across your Chaos rating and applied lethality. Keeping Corvo's observed presence minimal gives you a shot at the boast-worthy Ghost Achievement—where you complete Dishonored with no alerts—but the effort also ties heavily into the multiple detection and Chaos mechanics lurking beneath the game's steam-stained hood.

Earlier this month, Bethesda laid out details on the specific workings of detection and Chaos to help ambitious assassins attain the perfect balance of subtlety and savagery they prefer. Like a revelatory journal entry, the official forum post reveals all, but we've pasted the important bits below. Have a look:

How does the Chaos system work? How do I raise or lower the Chaos level that is displayed on the end mission stats screen?

Chaos is a value that is adjusted according to the actions of your character during gameplay. This system is a hidden mechanic and you will only see the Chaos rating displayed during the 'end mission' Stats screen.

Weepers do count for detection. They do raise the Chaos level if they are killed.

Kills by Rewired traps will contribute to your kill amounts and Chaos; that's Watchtowers, Arc Pylons, and Wall of Lights.

Rats, Hagfish and River Krust do not raise Chaos if killed. They also do not count towards detection of your character.

Wolfhound kills do not count towards Chaos, but they can detect your character and will count towards that. They can also discover bodies, as well as their corpse will count towards “bodies found”.

Your character's Chaos level will change the story outcome and lead to other various differences throughout gameplay, such as more enemy characters, more rats, or different scenes/environment items and conversations.

Basic rule is killing less than 20 percent of the characters in a Mission should allow the Low Chaos rating to be sustained.

I'm getting stats for bodies being found or killed when I've rendered NPCs unconscious, why?

Not hiding bodies well enough after choking them out or sleep darting them can sometimes lead to other characters finding them.

Unconscious characters won't survive a fall from a great height, or a slip into the water which will also result in a kill towards your character stats.

Situations that could lead to an NPC being killed inadvertently

Sleep Darting or Choking out an NPC and having them hit an object when falling, causing death

Sleep Darting or Choking out an NPC near a ledge and having them fall to cause death

Sleep Darting or Choking out an NPC and having them fall into water will cause drowning death

Sleep Darting or Choking an NPC and allowing them to fall down a long flight of stairs will sometimes cause them to die (possible with the stairs in the Overseer building)

Placing an unconscious NPC in water, or even near shallow puddles, can cause drowning death

Placing an unconscious body on un-even terrain near water can sometimes lead to the NPC slowly moving and falling into water, which would count as an NPC kill (in Prison Sewers for example)

Rendering an NPC unconscious near a damage source (such as a fireplace or lit grill) may cause the NPC to take damage and die

Leaving an unconscious NPC in the middle of the street or alley, where rats have access to the body, can result in clean-up which will count as a kill for the player

Accidentally casting Devouring Swarm near an unconscious NPC could cause the rats to clean up the body, counting as a NPC kill

Accidentally casting Windblast near an unconscious NPC could cause damage leading to NPC death

Having a Grenade, Springrazor or Whale Oil Battery explode near an unconscious NPC could cause splash damage resulting in NPC death

Throwing an unconscious NPC into a Wall of Light, or near and Arc Pylon would incinerate the NPC and count as a kill

Leaving unconscious NPCs in the area around the large door on which the player places the explosive device in Prison will cause the NPCs to die when the device goes off. This includes in and around the nearby dumpster and behind the consoles and gate switch across from the door on the upper level.

Rendering an enemy unconscious while fighting a nearby Tallboy can cause the Tallboy to stomp at the player, essentially killing the nearby unconscious NPC in the process

Rendering an enemy unconscious and having another enemy throw a projectile (such as fire bottle or grenade) at the player, can kill the nearby unconscious NPC

Leaving an NPC unconscious in the Brothel Steam room may cause “bite” damage due to hagfish in the center pool, killing the NPC

As a bonus, a player posted a short video walkthrough on surmounting a particularly tricky section of the latter portion of Corvo's journey that easily throws a Ghost run into peril due to a friendly NPC turning hostile after a scripted sequence. Check it out, but take heed of the massive spoilers revealed in the process.